DTC C1221-C1235. Chevrolet Tracker

For 1990-2009 cars only

Makes 🢒 Chevrolet 🢒 2001 🢒 Tracker - 4WD 🢒 Brakes 🢒 Antilock Brake System 🢒 DTC C1221-C1235

Circuit Description

As the wheel spins, the wheel speed sensor produces an AC signal. The EBCM uses the frequency of the AC signal to calculate the wheel speed.

Conditions for Running the DTC

C1221 through C1228

•	DTCs C1232 through C1235 are not set.

•	The brake pedal is not pressed.

•	The ABS is not active.

C1232 through C1235

The ignition is ON.

Conditions for Setting the DTC

C1221 through C1224

All of the following conditions exist for 2 seconds:

•	The suspect wheel speed equals zero.

•	The other wheel speeds are greater than 8 km/h (5 mph).

•	The other wheel speeds are within 11 km/h (7 mph) of each other.

C1225 through C1228

The EBCM detects a rapid variation in the wheel speed. The wheel speed changes by 16 km/h or more in 0.01 second. The change must occur 3 times with no more than 0.2 seconds between occurrences.

C1232 through C1235

One of the following conditions exists for 0.02 seconds or greater:

•	A short to voltage - the wheel speed sensor signal circuit and wheel speed sensor return circuit voltages are both greater than 4.25 volts.

•	A short to ground - the wheel speed sensor signal circuit and wheel speed sensor return circuit voltages are both less than 0.75 volts.

•	An open - the wheel speed sensor signal circuit voltage is greater than 4.25 volts and wheel speed sensor return circuit voltage is less than 0.75 volts.

Action Taken When the DTC Sets

The following actions occur:

•	The EBCM disables the ABS for the duration of the ignition cycle.

•	The ABS indicator turns ON.

Conditions for Clearing the DTC

•	The condition responsible for setting the DTC no longer exists and the Scan Tool Clear DTCs function is used.

•	100 drive cycles pass with no DTCs detected. A drive cycle consists of starting the vehicle, driving the vehicle over 16 km/h (10 mph), stopping and then turning the ignition OFF.

Diagnostic Aids

C1221 through C1224

Under the following conditions, 2 Wheel Speed Sensor Input is 0 DTCs are set:

•	The 2 suspect wheel speeds equal zero for 60 seconds.

•	The other wheel speeds are greater than 16 km/h (10 mph).

•	The other wheel speeds are within 11 km/h (7 mph) of each other.

Diagnose each wheel speed sensor individually.

C1225 through C1228

A possible cause of this DTC is electrical noise on the wheel speed sensor harness wiring. Electrical noise could result from the wheel speed sensor wires being routed to close to high energy ignition system components, such as spark plug wires.

C1232 through C1235

If the customer comments that the ABS indicator is ON only during moist environmental conditions (rain, snow, vehicle wash, etc.), inspect the wheel speed sensor wiring for signs of water intrusion. If the DTC is not current, clear all DTCs and simulate the effects of water intrusion by using the following procedure:

Spray the suspected area with a 5% saltwater solution. To create a 5% saltwater solution, add 2 teaspoons of salt to 354 ml (12 oz) of water.
Test drive the vehicle over various road surfaces (bumps, turns, etc.) above 40 km/h (25 mph) for at least 30 seconds.
If the DTC returns, replace the suspected wheel speed sensor or repair the wheel speed sensor wiring.
Rinse the vehicle thoroughly when completed.

Test Description

The numbers below refer to the step numbers on the diagnostic table.

This step tests the wheel speed sensor for the proper resistance value.

This step ensures that the wheel speed sensor generates the proper voltage.

Step

Action

Value(s)

Yes

Schematic Reference: Antilock Brake System Schematics

Did you perform A Diagnostic System Check - ABS?

Go to Step 2

Go to Diagnostic System Check - ABS

Install a scan tool.
Turn ON the ignition.
Set up the scan tool snap shot feature to trigger for this DTC.
Drive the vehicle at a speed greater than the specified value.

Does the scan tool indicate that this wheel speed DTC set?

8 km/h (5 mph)

Go to Step 3

Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems

Raise and support the vehicle. Refer to Lifting and Jacking the Vehicle in General Information.
Disconnect the wheel speed sensor connector.
Measure the resistance across the wheel speed sensor.

Does the resistance measure within the specified range?

1000-2000 ohms

Go to Step 4

Go to Step 8

Spin the wheel.
Measure the AC voltage across the wheel speed sensor.

Does the AC voltage measure greater than the specified value?

100 mV

Go to Step 5

Go to Step 8

Inspect for poor connections at the harness connector of the wheel speed sensor. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 10

Go to Step 6

Disconnect the EBCM harness connector.
Install the J 39700 universal pinout box using the J 39700-99 cable adapter to the EBCM harness connector only.
Test the wheel speed sensor circuits for the following:

•

An open

•	A short to ground

•	A short to voltage

•	Shorted together

Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 10

Go to Step 7

Inspect for poor connections at the harness connector for the EBCM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 10

Go to Step 9

Replace the wheel speed sensor. Refer to Front Wheel Speed Sensor Replacement or Rear Wheel Speed Sensor Replacement .

Did you complete the replacement?

Go to Step 10

Replace the EBCM. Refer to Electronic Brake Control Module Replacement .

Did you complete the replacement?

Go to Step 10

Use the scan tool in order to clear the DTCs.
Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.

Does the DTC reset?

Go to Step 2

System OK